Alloy having a low thermal expansion coefficient and a high spring bending limit

ABSTRACT

A material having a low thermal expansion coefficient (a linear thermal expansion coefficient of less than about 7 X 10 6/* C) and a high spring bending limit (more than about 64 kg./mm.2) has been demanded for mechanical or electronic device, physicochemical machine, industrial measurement device. A nickeliron alloy which consists essentially of 33-46 percent of Ni, 0.1-5 percent of Ti, 0.5-5 percent of Mo and the balance iron and has a linear thermal expansion coefficient of (2.2-7.1) X 10 6/* C and a spring bending limit of 64-125 kg./mm.2 is obtained as a material which suffices said demand.

United States Patent [72] Inventors ToshinarlHlrayama Kokubunji-shl;Hldeharu Ohara, Tokyo; Noboru Iehlyiuna, Kokubunil-shl, all 01 Japan[21] Appl. No. 814,995 [22] Filed Apr. 10, 1969 [45] Patented Dec. 28,1971 [73] Assignee Hitachi, Ltd.

Tokyo, Japan 32 Priority Apr. 17, 1968 J p [31] 43/ 25,221.

[54] ALLOY HAVING A LOW THERMAL EXPANSION COEFFICIENT AND A HIGH SPRINGBENDING Primary Examiner-L. Dewayne Rutledge Assistant Examiner-JosephE. Legru Attorney-Craig, Antonelli, Stewart & Hill ABSTRACT: A materialhaving a low thermal expansion coefficient (a linear thermal expansioncoefficient of less than about 7 10'/ C) and a high spring bending limit(more than about 64 kgJmm?) has been demanded for mechanical orelectronic device, physicochemical machine, industrial measurementdevice. A nickel-iron alloy which consists essentially of 33-46 percentof Ni, 0.1-5 percent of Ti, 0.5-5 percent of Mo and the balance iron andhas a linear thermal expansion coefficient of (2.2-7.1) X10'/ C and aspring bending limit of 64-125 ltgJmm. is obtained as a material whichsuffices said demand.

ALLOY HAVING A LOW THERMAL EXPANSION COEFFICIENT AND A HIGH SPRINGBENDING LIMIT This invention relates to a metal material which has a lowthermal expansion coefficient and a high spring bending limit.

Recently, the high mechanical accuracy of a mechanical or electronicdevice, a physicochemical machine, an industrial measurement device,etc. has been increasingly demanded and further the change intemperature of atmosphere in which devices are operated has beenincreased.

Therefore, a metal material to be used in the important parts of suchdevices as mentioned above is required to have a high strength andfurther a high spring bending limit which affects recoverity againstdeformation and a low thermal expansion coefficient which affects themechanical displacement with the change of temperature.

The term spring bending limit" used herein means a surface stressrequired for obtaining a strain at the center of a span of 0.005 cm. (or0.0025 cm.) when a plate span is bent and then restored. Said platespan, both end of which are freely supported, suffices the equationl-8,000 h (or 4,000 h) wherein h is the thickness and l is span length.

As the most familiar example, a cathode-ray tube for a color televisionwhich uses a shadow mask will be shown below.

ln FIGS. 1 and 2, 1 is a shadow mask, 2 is a frame which holds theshadow mask 1, 3 is a cathode-ray tube pannel (which is called pannelhereinafter) and 4 is a flat leaf spring (called leaf springhereinafter) which is located between said frame 2 and pannel 3 andwhich supports shadow mask 1 at pannel 3, and whose one end is fastenedto pannel 3 by mounting stud 5 and another end is fastened to frame 2 bywelding and the like.

Said mounting stud maintains said frame 2 at a correct position toassure that electron beams emitted from three electron guns accuratelyimpinge upon three colored fluorescence medium dots applied to theinside of the cathode-ray tube pannel through the shadow mask 1.

In this case, a difficulty exists in the fact that the thermal expansionof said leaf spring or pannel causes change in the relative positionbetween the fluorescence medium dots coated on the inside of the panneland holes of the shadow mask, due to which color misregistration occurson a screen. The term color misregistration" herein used means thechange of relative positions of said dots and holes.

However, among the parts on which the thermal expansion has effect, saidpannel and shadow mask cannot be changed in their qualities and sizesaccording to other conditions. Therefore, only the leaf spring can bedealt with in order to decrease color misregistration.

As the qualities of said leaf spring, the thermal expansion coefficientthereof should be as low as possible. Further, high strength and highrecoverity against mechanical deformation are desirable.

As an example, an experiment was conducted on a cathoderay for inch typecolor television to obtain the following results.

The length of change of the center position of the shadow mask was about26 1. depending upon the materials and under the temperature rise asmentioned in the above table I. In general, it is desirable to keep thechange of the center position of the shadow mask at less than l0 1 toreduce the color misregistration to such degree as is negligible.Therefore, the material of the leaf spring shown in table 1 is notsatisfactory.

According to the same example as mentioned above except that as the leafspring, Kovar (29 Ni-l7 Co-54 Fe by weight and linear thermal expansioncoefficient which is called merely thermal expansion coefficienthereinafter is about 5 l0'6/ C.), lnvar (36 %Ni-64 Fe by weight andthermal expansion coefficient about l.2 l0/ C.), or Super lnvar (32 Ni-5Co-63 Fe by weight and thermal expansion coefficient about 0.1Xl06/ C.)was used, the center position of the shadow mask shifts by about 7 p.0and no or substantially no color misregistration of the color televisionoccurred. Usually, such leaf spring is required to have a thermalexpansion coefficient of at most 8 l0'6/ C.

Regarding the spring bending limit of said materials, percent coldrolled plate of Kovar had about 65 kg./mm. after it was annealed at 550C., and 80 percent cold rolled plates of lnvar and Super lnvar had about40 kgjmm. and about 32 kg./mm., respectively, and merely about 60kg./mm. even after they were annealed at 550 C.

In general, said leaf spring is required to stand against a considerablylarge mechanical shift and experientially, it should have a springbending limit of at least 65 kg./mm. Said three materials have a springbending limit of merely 65 kg./mm. at most. In many cases, theconstructive materials of other mechanical or electronic device,physicochemical machine, industrial measurement device are also requiredto have a spring bending limit of more than 64 kg./mm.

The object of this invention is to provide a metal material which has alower thermal expansion coefficient and a higher spring bending limit.

A specific object of this invention is to provide a metal material whichhas a thermal expansion coefficient of less than 8Xl06/ C. andsimultaneously has a spring bending limit of more than 64 kg./mm.

FIG. 1 is a side view of a cathode-ray tube for color television whichis suitable for applying this invention and FIG. 2 is a cross-sectionalview at [I II.

The metal material for attaining the object of this invention consistsessentially of 33-46 percent of Ni, 0.1-5 percent of Ti, 0.5-5 percentof Mo and the balance Fe. It may additionally contain other elements insuch a small amount as does not greatly afi'ect the effect of thisinvention.

TABLE 2 Components (weight Thermal Spring percent) expansion bendingcoeflielent limit Ni Ti Mo Fe X10-/ C. (kg/mm 33 0. 1 0.5 Balance 4. 064 36 0.1 0.5 do.... 2.2 65 39 1.5 3.0 do. 4. 0 94 41 2.5 0.5 do.. 5.1108 41 2.5 5.0 .do 3,6 11!) 46 5.0 6.0 do 7.1

The above table 2 shows examples of the metal materials of thisinvention and each alloy having the indicated compositions was rolled ata reduction rate of 60-90 percent, then heated for 10 minutes-4 hours ata temperature of 500750 C., and subjected to ageing treatment. Thustreated metal materials of this invention showed a thermal expansioncoefficient of (2.27.l)Xl0/ C. and a spring bending limit of (64-125)kgjmmf. Thus, it was recognized that according to this invention, aconspicuously excellent alloy which has a low thermal expansioncoefficient and simultaneously has a high spring bending limit can beprovided.

In this invention, when the content of Ni is less than 33 percent, thethermal expansion coefficient of the alloy increases and simultaneouslythe spring bending limit conspicuously decreases and when the content ofNi is more than 46 percent, a high spring bending limit is attained,while the thermal expansion coefficient remarkably increases.

Addition of Ti in an amount of 0.1-5.0 percent, can increase the springbending limit when Ni is added in the said range of the content withinwhich a low thermal expansion coefficient can be attained, but when thecontent of Ti is less than 0.1 percent, said increase of the springbending limit is only a little and when more than 5 percent, the thermalexpansion coefficient increases to result in undesirable effect.

Addition of M in an amount of 0.5- percent increases the spring bendinglimit with a low thermal expansion coefficient, but said increase of thespring bending limit is smaller than that due to Ti. However, saidaddition of Mo results in the rise of recrystallization temperature ofthe alloy and, therefore, the alloy can be heat treated at a highertemperature and thus the time required for ageing treatment can beshortened.

In this invention, when a high spring bending limit (more than 90kg./mm. is especially required, a composition of 39-46 percent of Ni,1.5-5.0 percent of Ti and 0.5-5.0 percent of M0 is suitable and when alow thermal expansion coefficient (less than 5.0X/ C.) is especiallyrequired, a composition of 33-41 percent of Ni, 0.1-2.5 percent of Tiand 0.5-5.0 percent of M0 is suitable.

In order to obtain an alloy having a high spring bending limit (morethan 90 kgJmmF) and a low thermal expansion coefficient (less than5.0Xl0 C.), a composition of 39-41 percent of Ni, 1.5-2.5 percent of Tiand 0.5-5.0 percent of M0 is the most suitable.

Of course, it is needless to say that the thermal expansion coefficientand the spring bending limit of the metal material of this inventionwhich are embodied by said composition ranges are varied depending uponthe reduction rate and the conditions of heat treatment.

As mentioned above, the metal material of this invention has anextremely low thermal expansion coefficient and further has a highspring bending limit. Thus, according to this invention, a difficultythat the conventional metal material has not been above to possess bothof said properties can be overcome.

Therefore, without an example of a cathode-ray tube for a colortelevision which uses said shadow mask, this invention provides amaterial which is extremely useful for other various equipments,devices, etc. as mentioned above which requires maintenance of a highaccuracy in an atmosphere in which temperature widely changes and a highrecoverity against the mechanical deformation.

1n this specification, the percentage which indicates the content ofthecomponents is by weight.

What we claim is:

l. A metal material having a low thermal expansion coefficient and ahigh spring bending limit, which consists essentially of 33-46 percentweight percent of Ni, 0. l-5 weight percent ofTi, 0.5-5.0 weight percentof Mo and the balance Fe.

2. A metal material according to claim I, which consists essentially of39-46 weight percent of Ni, 1.5-5 weight percent of Ti, 0.5-S weightpercent ofMo and the balance Fe.

3. A metal material according to claim 1, which consists essentially of33-41 weight percent of Ni, 0.1-2.5 weight percent of Ti, 0.5-5 weightpercent of Mo, and the balance Fe.

4. A metal material according to claim 1, which consists essentially of39-41 weight percent of Ni, 1.5-2.5 weight percent ofTi, 0.5-5 weightpercent of Mo and the balance Fe.

5. An alloy having a linear thermal expansion coefficient of less thanabout 8Xl0/ C. and a high spring bending limit of greater than about 64kg./mm. which consists essentially of about 33 to 46 weight percent ofNi, about 0.1 to 5 weight percent of Ti, about 0.5 to 5.0 weight percentof Mo and the balance Fe.

6. The alloy of claim 5 having a linear thermal expansion coefficient ofabout 2.2 to 7. l Xl0'/ C. and a spring bending limit of about 64 to 125kg./mm.

7. An alloy having a low thermal expansion coefficient and a high springbending limit of greater than about kg./mm. which consists essentiallyof about 39 to 46 weight percent of Ni, about 1.5 to 5.0 weight percentof Ti, about 0.5 to 5.0

weight percent of Mo and the balance Fe.

8. An alloy having a low thermal expansion coefiicient of less thanabout 5.0X10' C. and a high spring bending limit which consistsessentially of about 33 to 41 weight percent of Ni, about 0.1 to 2.5weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and thebalance Fe.

9. An alloy having a low thermal expansion coefficient of less thanabout 5.0X10 C. and a high spring bending limit of greater than about 90kg./mm. which consists essentially of about 39 to 41 weight percent ofNi, about 1.5 to 2.5 weight percent of Ti, about 0.5 to 5.0 weightpercent of Mo and the balance Fe.

2. A metal material according to claim 1, which consists essentially of39-46 weight percent of Ni, 1.5-5 weight percent of Ti, 0.5-5 weightpercent of Mo and the balance Fe.
 3. A metal material according to claim1, which consists essentially of 33-41 weight percent of Ni, 0.1-2.5weight percent of Ti, 0.5-5 weight percent of Mo, and the balance Fe. 4.A metal material according to claim 1, which consists essentially of39-41 weight percent of Ni, 1.5-2.5 weight percent of Ti, 0.5-5 weightpercent of Mo and the balance Fe.
 5. An alloy having a linear thermalexpansion coefficient of less than about 8 X 10 6/* C. and a high springbending limit of greater than about 64 kg./mm.2 which consistsessentially of about 33 to 46 weight percent of Ni, about 0.1 to 5weight percent of Ti, about 0.5 to 5.0 weight percent of Mo and thebalance Fe.
 6. The alloy of claim 5 having a linear thermal expansioncoefficient of about 2.2 to 7.1 X 10 6/* C. and a spring bending limitof about 64 to 125 kg./mm.2.
 7. An alloy having a low thermal expansioncoefficient and a high spring bending limit of greater than about 90kg./mm.2 which consists essentially of about 39 to 46 weight percent ofNi, about 1.5 to 5.0 weight percent of Ti, about 0.5 to 5.0 weightpercent of Mo and the balance Fe.
 8. An alloy having a low thermalexpansion coefficient of less than about 5.0 X 10 6/* C. and a highspring bending limit which consists essentially of about 33 to 41 weightpercent of Ni, about 0.1 to 2.5 weight percent of Ti, about 0.5 to 5.0weight percent of Mo and the balance Fe.
 9. An alloy having a lowthermal expansion coefficient of less than about 5.0 X 10 6/* C and ahigh spring bending limit of greater than about 90 kg./mm.2 whichconsists essentially of about 39 to 41 weight percent of Ni, about 1.5to 2.5 weight percent of Ti, about 0.5 to 5.0 weight percent of Mo andthe balance Fe.